A few basic questions (VBOs / performance)

[infernal]

Hi there,

here is yet again another opengl newbie asking weird questions, so please bear with me

I have started to use interleaved VBOs (TTNNNVVV) but was unaware that I would have to add a normal for every vertex.
Is this the regular way of using VBOs or is it somehow possible to define a face normal once for several following vertices in a VBO (NNNTTVVVTTVVVTTVVV...)?
I would imagine that using an identical normal repeatedly for the vertices of a quad / triangle slows things down which I want to avert.

As a second question: I am partitioning my game world and storing the data subsets into several VBOs so that I only need to update and resend a smaller VBO on a change. Is this ok or would you recommend me to minimize the VBO amount?

I am also minimizing the amount of to-be-rendered quads by merging several adjacent quads with the same normal. Is it wasted time to pursue such optimizations? Should I rather trust in the rendering speed and built-in optimizations of the graphics card in comparison to (crude) homemade heuristics with a high overhead?